Directory assistance services are provided to help telephone subscribers locate telephone directory numbers of other subscribers. The services are customarily provided by a directory assistance operator connected to the requesting customer via a switching system. Early designs of directory assistance systems required operators to refer to books and file cards to find the desired directory numbers. As directory assistance traffic increased, more efficient and automated techniques and systems were introduced to aid operators in furnishing the required service.
One directory assistance system currently in commercial use, the No. 5 Crossbar Automatic Call Distribution System manufactured by AT&T Technologies, Inc., provides each directory assistance operator with a terminal for communicating with a directory assistance computer. In this system, a subscriber's call requesting directory assistance is routed via a special purpose incoming trunk which is connected to a switching network, for establishing a switchable voice connection to an operator, and is permanently connected to an audio response unit. For each assistance call, the operator verbally requests data regarding the subscriber to be called and, upon its receipt, communicates with a directory assistance computer and concurrently controls a connection of the incoming trunk to the computer terminal. Next, the audio response unit receives data from a switching network controller that a particular incoming trunk has been connected to the computer terminal serving that operator. When the computer has located the correct directory number, it sends a message to the audio response unit causing it to generate an audible directory announcement representing the desired directory number and transmits that voice message to the customer via the permanent path to the previously identified incoming trunk.
Such an arrangement is expensive because it requires the use of expensive special purpose trunks to connect the customer to the switching network and separately to the audio response unit. Further, the audio response unit requires a large number of output ports permanently connected to each of the special purpose trunk circuits. A recognized problem of the prior art is that such computerized directory assistance systems need costly complicated and separate control units for both the switching network and the audio response unit, as well as separate connections to the switching network and the audio response unit. The assistance equipment unit additionally can serve only one call at a time per port with its inherent delays, particularly, for lengthy operation communications.